The present invention relates to a method of recovering boric acid.
It has been well known to produce cyclohexanol by oxidizing cyclohexane in the presence of a catalyst of boric acid.
In the reaction, the reaction mixture containing cyclohexanol, the catalyst of boric acid, the unreacted cyclohexane, and other organic by-products, has been obtained.
The reaction mixture has hydrolyzed and separated to the oil phase containing cylcohexanol and the water phase containing boric acid.
The water phase has been usually concentrated by heating to precipitate crystals of boric acid and the boric acid has been recovered. In this case, the recovery ratio has been increased by increasing the degree of the condensation. However, when the degree of the condensation is too high, the viscosity of mother liquor has been too high and the separation of the precipitated crystals has not been easy and the amount of the mother liquor adhered on the crystals has been increased whereby the purge of the organic materials has not been easy. Accordingly, the concentration has been limited and the complete recover of boric acid has not been attained.
Since the complete recovery of boric acid has not been attained, the lost of the catalyst has been found and the treatment of the mother liquor after recovering boric acid has not been easily attained. That is, the organic by-products have been remained at relatively high ratio. It is preferable to concentrate and dry the mother liquor and to burn the organic materials. However, when boric acid is included in the organic materials, the lining bricks of the combustion furnace are damaged and the accident of explosion may be considered and the combustion treatment could not been carried out. Accordingly, it has been obliged to treat the mother liquor by the waste water treatment such as the activated sludge process.
Heretofore, certain improved methods have been proposed, however, any satisfactory method has not been found.